On the formation of μ and ζ phases in the AgAl system by mechanical alloying

Abstract

Pure Ag and Al powders have been mechanically alloyed in a Spex mill. Four selected nominal compositions Ag 1− x Al x ( x = 0.20, 0.23, 0.26 and 0.37) were investigated by X-ray diffraction and differential scanning calorimetry, after being subjected to different times of ball milling. In all four selected compositions, the close-packed hexagonal intermediate ζ phase and the f.c.c. α phase (Ag-based solid solution) formed together during the first hour of milling, but subsequently the α phase disappeared during continued milling except in the two alloys corresponding to 26 at.% Al and 37 at.% Al where the ζ phase is the equilibrium phase. With continued milling, the complex cubic μ phase formed in the alloys of nominal composition 20, 23 and 26 at.% Al where it is expected in equilibrium alloys. No amorphous phases have been observed in the mechanically alloyed powders in this system.